The Object Technology Framework (OTF) includes our continued work on class libraries for manipulating molecular data. The OTF is designed and implemented using an object-oriented paradigm that organizes the functionality into components within a modular and extensible framework. Applications can be created by combining selected prefabricated components with a small amount of custom code, making development of new analysis tools much easier. The OTF has been used locally to develop applications for generating idealized collagen models, computing dihedral angles in proteins, and computing Gaussian neighborhood values of amino acids in proteins. All these applications were implemented in a short time, most of which was spent designing and coding application-specific algorithms. The improvement in coding efficiency stems from the use of the prefabricated components and the organization tools of the OTF. A new release of the OTF was made available on the Internet via anonymous ftp in November, 1996. This latest release includes a redesign of the component hierarchy as well as a new program for managing these components. As with all of our software, the OTF is distributed as documented source code. Up-to-date documentation of the OTF is also available, as of December 1997, via the World Wide Web at http://cgl.ucsf.edu/home/otf.